1. Field of the Invention
This invention relates generally to electrical protective devices and, more particularly, to a device for interrupting electrical current to an electrical appliance and the like for excess values of electrical current.
2. Description of the Prior Art
When most electrical appliances are connected to the usual wall receptacle they are connected electrically to a power line without any protection against surges of electric current which might seriously damage them. Generally, the only safety devices in these power lines are fuses or circuit breakers which are adapted to burn out when the lines that they service sense a current overload. These devices are not adequate to protect appliances since a current overload which might be less than that required to open the circuit breaker or burn out a fuse might still be great enough to damage the appliance. Typically, these current overloads result from voltage surges caused by lightning striking the structure in which these appliances are housed, or by striking an exposed power line.
A solution to this probelm is the isolator presented by James F. Worthington in U.S. Pat. No. 3,539,961. The isolator had a male plug member and a female receptacle electrrically interconnected by fusible wire. An arc plate, connected to a third prong, is disposed adjacent the male prong members of the isolator so when current in excess of a predetermined value flows through the device, the fuse wire is burned out and the current is carried by the arc plate to ground thereby effectively isolating the appliance and saving it from damage. In actual practice, the fusible wire did not consume itself rapidly enough to prevent excess, damaging current from reaching the appliance. Also, the fusible wire was not self-restoring and needed replacement by a technician. Thus, there exists a need for a current interrupter for appliances which is self-restoring and fast acting.